While driving to work, a 27-year-old man had a motor vehicle collision; when the police attended the scene they found him to be drowsy and immediately called an ambulance. The man, who was previously healthy, presented with slurred speech and right-sided weakness. Earlier that day, he had complained to his mother that he wasn’t feeling well, and some mild heaviness and numbness had developed on his right side. The patient denied any injury to the head from the collision. His vital signs were within normal limits, with a blood pressure of 115/59 mm Hg. The patient was drowsy. There was evidence of moderate right-sided hemiparesis, mild reduction in sensation to pinprick on the right, mild receptive and expressive dysphasia, and severe dysarthria.